It's not possible to install over xp, so you lose everything. You must backup your personal files and do a Custom install (clean install.) Directions on the installation disk or at the win 7 site. You can use the Upgrade disk to do a clean install. With XP it's best to run the Windows Upgrade Advisor to make sure your computer can run Win 7.

I installed a new hard drive in my machine and installed Windows 7 on to that. To switch between my XP and Win 7 installations I just have to change the HDD order in the BIOS during the boot up process. A trifle clunky but it works.

Is it possible to install win7 over windows xp. What am i going to lose?

MaryG's suggestion to use the Windows 7 Upgrade Advisor, free from Microsoft, is "bang on". W7UA will tell you if going to W7 is even an option. That said:

There is no XP to "W7 Upgrade" Option, so you must do a W7 "Custom Install", which formats the XP partition, and wipes out all your personal data (so, Back Up XP, first!), unless you choose to set up a dual-boot configuration. An XP back up is the only way to ensure that you won't lose anything. The full procedure, including how to do the back up, is printed (on paper) in the W7 Upgrade kit.

Side Bar:

The solution to Mike Rule's BIOS Boot issue is a little GEM called EasyBCD (free). It puts XP into the W7 Boot Loader screen. Google for it...

FYI: You can still use a W7 Upgrade kit for use with XP, there is no need to BUY a full version of W7. In fact, there's an article on http://www.windowssecrets.com that explains how to do a Vista to W7 Upgrade, and then, convert that to a full Custom Install without losing all your Vista stuff, legally!

Re: JoeP's comment about voiding previous Activation Codes, that can happen when Upgrading to W7, but the "jury's still out" when using the Custom Install, despite what Microsoft implies. http://www.windowssecrets.com discusses the confusion over this issue, too. This is not an attempt at 'flaming", but for clarification.

There is no XP to "W7 Upgrade" Option, so you must do a W7 "Custom Install", which formats the XP partition, and wipes out all your personal data (so, Back Up XP, first!), unless you choose to set up a dual-boot configuration. An XP back up is the only way to ensure that you won't lose anything. The full procedure, including how to do the back up, is printed (on paper) in the W7 Upgrade kit.

This isn't entirely correct, by default it doesn't format the partition. You have to opt to format it, and it will warn you about losing data. If you don't, it will copy your old installation of windows to a folder called "c:\windows.old", after installing Win7 you can then go though that folder and pull out your data.

That said, of course things can happen and, regardless of the upgrade, it is always important to back up any data you don't want to lose so it already should be backed up.

If you have critical data and software in Windows XP, back it up before doing anything, better safe than sorry.

The path of least resistance would be to clean up your hard drive and make room for a clean install of Windows 7.

Then you can experiment with software and data in Win 7 while having a fallback to your Win XP installation.

The reason MS doesn't allow for inplace upgrades in WinXP is due to all the nightmares possible with hardware
and software. And if your computer is more than 3-4 years old, it most likely doesn't have the power necessary
to run Win 7 anyway. It might run, but it won't be pretty.

I would do a clean install even if I was upgrading Vista, it's just a better scenario on every level.

After about 100 installs/upgrades I can recommend that you have at least dedicated video ram, or better yet a Video
Card with onboard ram, 4 gigs of fastest ram your computer will take. A duo processor of 2.0 and above processor
helps a lot too.

Likewise, I installed Windows 7 Ultimate, X86 on my Acer Aspire ONE Netbook.
I have an upgraded version with 1.5gigs of ram and a 160 gig HD so Win-7 actually ran pretty good,
and the installer even came up with 'workable' drivers for the video, lan, etc.
But it was just a "Test" and after a week or two, I wanted my Windows XP back.

Well, I've been down this "I'm just testing" road a time or two before, so,
before I did anything else, I repartitioned my little Netbook HD with
Partition Magic 8 and I made a "Partition to Image" copy of C: to D:
using Ghost 11.5, booting from a Flash Drive.

So now, with XP safely backed up to D:, I set about installing Win-7 from a DVD
in an external DVD drive.
When I finally got sick of Win-7, a six minute RESTORE of my XP image, put
me right back in business with Windows XP. I don't think I'll be doing that again.

Now, I've also got XP (two different versions) and Win-7 installed on my desktop.
BUT, each OS is on its own HD. So with three OS's and one storage drive, I've got
four SATA II drives in my Desktop PC.
Unlike the factory made PC's like HP, Dell, etc., many home made PC's have a much
more versatile BIOS on their motherboards.

I have two PC's that I built, , one is almost nine years old now with an Asrock mobo and
the other one is only about three years old, with an MSI mobo and they both give me a
nice little boot menu when I press the F11 key during the boot process.
It's F12 on my little Acer Netbook.

I got my Windows 7 upgrade disk from Dell for free. I followed the directiions to use the MigWiz to save all my data and expected to do a clean install over my Windows XP on my Dell laptop. I crossed my fingers and put in the Win 7 disc and started the process. Lo and behold, no formatting, not loss of data, just a new OS and a great working system. ALL my old files and programs are now in a folder ' Windows.old '. All my data files are still in their respective folders and come up when selected. Not only that, but all my old programs still run when I go into windows.old and find the executable. No problems at all. Let me just say that I am more than pleasantly surprised.

I have since moved all the files I want to keep out of the old locations and into my new library. Programs that I want to use have been freshly reinstalled but there are still some that are in their old locations and I just put a shortcut into a new folder on the desktop to get to them. All their settings and passwords are still intact too.

Did I miss something along the way? Did I just get lucky? How come nobody else seems to have noted this as an option for an XP upgrade?

I installed a new hard drive in my machine and installed Windows 7 on to that. To switch between my XP and Win 7 installations I just have to change the HDD order in the BIOS during the boot up process. A trifle clunky but it works.

Install your Win 7 on a new HDD. Install everything fresh and you'll lose all the ** STUFF ** (i.e., spring cleaning) that you've been accumulating for years and there's no other way to get rid of it. You can install the old disk as a 2nd drive &/or get a USB HDD drive shell for it & keep all of your old stuff that way. After a few months of confidence with the new system, FDisk & format the old drive and use for back up or spare.